//! 简化的Flight SQL服务实现
//! 
//! 提供基础的Flight SQL协议支持

use std::pin::Pin;
use std::sync::Arc;
use futures::Stream;
use tonic::{Request, Response, Status};
use arrow_flight::{
    flight_service_server::FlightService, Action, ActionType, Criteria, Empty, FlightData,
    FlightDescriptor, FlightInfo, HandshakeRequest, HandshakeResponse, PutResult, SchemaResult,
    Ticket, Result as FlightResult,
};
use arrow::record_batch::RecordBatch;
use arrow::ipc::writer::{IpcDataGenerator, IpcWriteOptions};
use arrow::datatypes::Schema;
use data_gateway_kernel::DataGatewayKernel;
use crate::{FlightSqlError, Result};
use async_stream::stream;

/// 简化的Flight SQL服务
pub struct SimpleFlightSqlService {
    /// 内核引用
    kernel: Arc<DataGatewayKernel>,
}

impl SimpleFlightSqlService {
    /// 创建新的Flight SQL服务
    pub fn new(kernel: Arc<DataGatewayKernel>) -> Self {
        Self { kernel }
    }
    
    /// 将RecordBatch转换为FlightData
    fn record_batch_to_flight_data(&self, batch: &RecordBatch) -> Result<FlightData> {
        let mut data_gen = IpcDataGenerator::default();
        let options = IpcWriteOptions::default();
        
        // 生成schema数据
        let schema_data = data_gen.schema_to_bytes_with_dictionary_tracker(
            batch.schema().as_ref(),
            &mut Default::default(),
            &options,
        )?;
        
        // 生成batch数据
        let (_, batch_data) = data_gen.encoded_batch(
            batch,
            &mut Default::default(),
            &options,
        )?;
        
        Ok(FlightData {
            data_header: schema_data.ipc_message,
            data_body: batch_data.arrow_data,
            app_metadata: bytes::Bytes::new(),
        })
    }
}

#[tonic::async_trait]
impl FlightService for SimpleFlightSqlService {
    type HandshakeStream = Pin<Box<dyn Stream<Item = Result<HandshakeResponse, Status>> + Send>>;
    type ListFlightsStream = Pin<Box<dyn Stream<Item = Result<FlightInfo, Status>> + Send>>;
    type DoGetStream = Pin<Box<dyn Stream<Item = Result<FlightData, Status>> + Send>>;
    type DoPutStream = Pin<Box<dyn Stream<Item = Result<PutResult, Status>> + Send>>;
    type DoActionStream = Pin<Box<dyn Stream<Item = Result<FlightResult, Status>> + Send>>;
    type ListActionsStream = Pin<Box<dyn Stream<Item = Result<ActionType, Status>> + Send>>;
    type DoExchangeStream = Pin<Box<dyn Stream<Item = Result<FlightData, Status>> + Send>>;

    async fn handshake(
        &self,
        _request: Request<tonic::Streaming<HandshakeRequest>>,
    ) -> std::result::Result<Response<Self::HandshakeStream>, Status> {
        let output = stream! {
            yield Ok(HandshakeResponse {
                protocol_version: 0,
                payload: bytes::Bytes::from("Flight SQL Server Ready"),
            });
        };
        Ok(Response::new(Box::pin(output)))
    }

    async fn list_flights(
        &self,
        _request: Request<Criteria>,
    ) -> std::result::Result<Response<Self::ListFlightsStream>, Status> {
        let output = stream! {
            // 返回空的flight列表
        };
        Ok(Response::new(Box::pin(output)))
    }

    async fn get_flight_info(
        &self,
        request: Request<FlightDescriptor>,
    ) -> std::result::Result<Response<FlightInfo>, Status> {
        let descriptor = request.into_inner();
        
        // 简单的SQL查询处理
        if let Some(cmd) = descriptor.cmd.as_ref() {
            if let Ok(sql) = String::from_utf8(cmd.to_vec()) {
                // 创建基础的FlightInfo
                let flight_info = FlightInfo {
                    schema: bytes::Bytes::new(),
                    flight_descriptor: Some(descriptor),
                    endpoint: vec![],
                    total_records: -1,
                    total_bytes: -1,
                    ordered: false,
                    app_metadata: bytes::Bytes::new(),
                };
                
                return Ok(Response::new(flight_info));
            }
        }
        
        Err(Status::invalid_argument("Invalid flight descriptor"))
    }

    async fn get_schema(
        &self,
        _request: Request<FlightDescriptor>,
    ) -> std::result::Result<Response<SchemaResult>, Status> {
        // 返回空schema
        let schema_result = SchemaResult {
            schema: bytes::Bytes::new(),
        };
        Ok(Response::new(schema_result))
    }

    async fn do_get(
        &self,
        request: Request<Ticket>,
    ) -> std::result::Result<Response<Self::DoGetStream>, Status> {
        let ticket = request.into_inner();
        
        // 解析SQL查询
        if let Ok(sql) = String::from_utf8(ticket.ticket.to_vec()) {
            let kernel = self.kernel.clone();
            
            let output = stream! {
                // 创建查询
                let query = data_gateway_kernel::Query::sql(sql);
                
                // 执行查询
                match kernel.execute_query(query).await {
                    Ok(result) => {
                        if let Some(batches) = result.as_arrow() {
                            for batch in batches {
                                match self.record_batch_to_flight_data(&batch) {
                                    Ok(flight_data) => yield Ok(flight_data),
                                    Err(e) => yield Err(Status::internal(format!("转换错误: {}", e))),
                                }
                            }
                        }
                    }
                    Err(e) => {
                        yield Err(Status::internal(format!("查询执行错误: {}", e)));
                    }
                }
            };
            
            return Ok(Response::new(Box::pin(output)));
        }
        
        Err(Status::invalid_argument("Invalid ticket"))
    }

    async fn do_put(
        &self,
        _request: Request<tonic::Streaming<FlightData>>,
    ) -> std::result::Result<Response<Self::DoPutStream>, Status> {
        let output = stream! {
            yield Ok(PutResult {
                app_metadata: bytes::Bytes::new(),
            });
        };
        Ok(Response::new(Box::pin(output)))
    }

    async fn do_action(
        &self,
        _request: Request<Action>,
    ) -> std::result::Result<Response<Self::DoActionStream>, Status> {
        let output = stream! {
            yield Ok(FlightResult {
                body: bytes::Bytes::from("OK"),
            });
        };
        Ok(Response::new(Box::pin(output)))
    }

    async fn list_actions(
        &self,
        _request: Request<Empty>,
    ) -> std::result::Result<Response<Self::ListActionsStream>, Status> {
        let output = stream! {
            // 返回空的action列表
        };
        Ok(Response::new(Box::pin(output)))
    }

    async fn do_exchange(
        &self,
        _request: Request<tonic::Streaming<FlightData>>,
    ) -> std::result::Result<Response<Self::DoExchangeStream>, Status> {
        let output = stream! {
            // 返回空的exchange流
        };
        Ok(Response::new(Box::pin(output)))
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use tokio_test;

    #[tokio::test]
    async fn test_simple_flight_service_creation() {
        let kernel = Arc::new(DataGatewayKernel::new().await.unwrap());
        let service = SimpleFlightSqlService::new(kernel);
        
        // 测试服务创建成功
        assert!(true);
    }
}
